The present invention relates to a gauge for gauging the position of the working elements of a movable tool of a power tool.
Power tools, such as table saws, radial arm saws, routers, milling machines, and drill presses include a mechanism for adjusting the depth and, often, the angle of the cut or other alteration of the work produced by the tool. The adjustment mechanism changes the position or plane of operation of a working element of the tool (such as the cutting edge of a tooth) relative to a locating datum that positions the work. The adjustment mechanism may include an indicator of the height or angle of the working elements of the tool relative to the machine""s table or other work locating datum. However, some power tools do not include such an indicator. Further, slack or wear in the adjustment mechanism and variations in the tool size or depth of insertion in the tool holder often make the reliability and accuracy of these built-in tool position indicators suspect. Therefore, despite the presence of built-in tool position indicators, power tool users often check the position of a working element of the tool by direct measurement. However, parallax and the arrangement of the elements of the power tool often make accurate measurement with a ruler or other measuring device difficult.
For greater accuracy and convenience, gauges have been developed that are supported by the table or work locating datum of the power tool and directly contact the working element of the tool. Gibson, U.S. Pat. No. 5,168,637; discloses a measuring device with a vertically movable head mounted on a column. The base of the column is placed on the table of a saw and the head is brought into contact with a tooth of the saw blade. The distance between the cutting edge of the tooth and the table is read from a scale attached to the column. Such an infinitely adjustable measuring device can be quite accurate if the moving parts of the gauge fit well and if the scale gradations are small. However, the close manufacturing tolerances and substantial structure required for accurate gauging can result in an expensive gauge and the structure of the gauge may interfere with machine elements, especially when the machine has an over-the-work structure. Often only a limited number of discrete, accurate gauging positions are sufficient for machine set up making a precision, infinitely adjustable gauge an unnecessary expense. Further, determining when the working element has contacted the gauging reference requires careful continuous inspection of the gauging reference or the area of contact of the gauge base with the machine tool.
A gauge providing a single, fixed gauging reference is disclosed by Boucher et al., in U.S. Pat. No. 5,934,973. This gauge is attached to the side of the table of a wafer cutting saw and gauges the minimum acceptable distance between the table and the cutting elements of the saw blade. When the saw blade contacts the top of the gauge, a piezoelectric switch is deflected producing an electrical signal. The signal is used to alert the machine operator that the saw blade has reached the minimum desired working height above the table. While a gauge with single gauging reference attached to a power tool is acceptable for a singular use in a production environment, it is not particularly useful in setting up a number of power tools in a shop. The gauge includes a convenient indicator of tool position. However, the accuracy of the gauge is subject to the amount and consistency of deflection of the gauging reference required to actuate the signaling device. This gauge utilizes an expensive piezoelectric switch to achieve the consistency of gauging reference deflection required for accurate measurement.
What is desired, therefore, is an inexpensive and easily used gauge for accurately gauging the relative position of a working element of a tool relative to the work locating datum of a power tool.
The present invention overcomes the aforementioned drawbacks of the prior art by providing a gauge for gauging a relative position of a working element and a locating datum of a power tool comprising a conductive gauge reference arranged for selective engagement with the working element at a spaced relation to the locating datum; a contact insulated from the gauge reference and arranged for conductive engagement with the working element; and an indicator of conduction between said gauge reference and said contact. An LED provides a clear indication to the user that the working element of the tool is in contact with the gauging reference and, therefore, adjusted to the desired position. The LED is part of a simple open circuit that is closed by conductive engagement between the tool, through the conductive gauge reference, and a second electrical terminal of the open circuit. The gauge is of inexpensive construction and can include a plurality of fixed gauging references or adjustable gauging references. The gauge can be used with a number of power tools.
A gauge is also provided for gauging the angular position of the working element of a tool relative to a locating datum comprising a conductive gauge reference in spaced relation to the locating datum and arranged for selective engagement with the tool in a plane parallel to the plane of operation of the working elements of the tool; a contact insulated from the gauge reference and arranged for conductive engagement with the tool; and an indicator of conduction between the gauge reference and the contact.
The foregoing and other objectives, features and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings.